Maturation and quality of seeds of an endangered tropical palm species (Euterpe edulis Martius) assessed by imaging and X-ray densitometry

Abstract

Abstract Euterpe edulis Martius is an endangered palm species that grows in the Atlantic Forest and the Cerrado of South America. Economic exploitation of its antioxidant-rich fruits could ensure the sustainable management of this species. However, this relies on the rapid selection of high-quality seeds from which to derive seedlings. The objective of this study was to investigate the maturation of E. edulis seeds using image analysis and X-ray densitometry. Fruits were harvested from ten matrices at different stages of maturation, from 94 days after anthesis (DAA) to 290 DAA. Seed dry mass, water content, germination, vigor, and density were quantified at each stage. At the same time, seeds were analyzed by GroundEye® imaging, radiography, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The highest dry mass was detected 255 DAA (0.83 g), in vitro germination began 115 DAA and achieved 100% from 150 DAA, and maximum vigor was observed 164 DAA, whereby 100% of seedlings appeared normal. X-ray imaging revealed dehydrated seeds and small mechanical damage, such as cracking of the pericarp. X-ray densitometry revealed that seed density increased considerably 185 DAA. SEM/EDS detected changes between maturation stages, such as the accumulation of K and Si, in the mesocarp and endocarp. Overall, E. edulis seeds presented maximum in vitro germination, vigor, percentage of normal seedlings, and physicochemical qualities 164 DAA (green epicarp), which corresponds to 126 days earlier compared with the fruits harvested 290 DAA (black epicarp) for ex vitro germination.